/Engine/Plugins/FX/Niagara/Source/NiagaraEditor/Public/ViewModels/NiagaraSystemViewModel.h
This is specifically for UI with some unique behavior. If at least 1 selected emitter is currently not in solo-mode, we assume the user wants to override the 'solo selection' so that all currently selected emitters enter solo mode Since the UI functions can be activated without selection (i.e. clicking 'Isolate' in a overview node won't select the emitter), we always have to specify the guid of the emitter that triggered the call. This is so we can work on all selected emitters + the emitter we clicked Isolate on.
void ToggleIsolateEmitterAndSelectedEmitters ( [FGuid](API\Runtime\Core\Misc\FGuid) OriginEmitter )